Hi
I would like to know if there is a way to create a alpha mask with transparency like the ones we get in physical render.
Have a look at the demo image I rendered with physical.
If there is a way, how can I get the same output?
Thank you
Sure, why not. Have you done any experimenting with Corona yet?
Otherwise, to mimic/replicate as close as possible, test file is a must.
Yes I have done, that is why I am asking if anyone had the same trouble in past and could tell me a way of doing / extract a similar output.
Sure, a scene file is always useful. 
transparecy_test.c4d (592 KB)
I thought I was going to fly in here and say, “It’s easy. Just do what I say,” but I wasn’t able to get the same result either.
At the moment that’s not possible in Corona, however this feature is highly desirable by many users and devs are determined to implement it sometime in the future. Meanwhile you can vote for its faster implementation here: https://forum.corona-renderer.com/ The most wanted feature? and track its status here: Trello The roadmap is for 3ds max, but almost any feature that will be implemented here, soon will appear in C4D too.